It could be any number of things. Would need more info and uploading flight logs could be a good place to start. Healthydrones.com is an easy way to do this and share the info.

It could be a prop balancing issue as well, of calibration of compass or imu. Lots of potential causes. What firmware are you on, any control inputs, any possible prop strikes prior to flight that could cause an imbalance?

Make sure there is no damage or deformity to props. Calibrate RC & IMU in Go app. Make sure aircraft is perfectly level during IMU calibration. Calibrate compass once outside. I suggest auto-takeoff on soft grass. Might even want to tether it just in case.

Probably not, but if the controls are in mode 1 (right stick is throttle) and you are expecting mode 2 (left stick is throttle), if you give it forward pitch at take off rather than throttle, the phantom will pitch over. It would most likely be forward, but after it rolls and is unstable, who knows if it ends up going forward or left.

Other common problem while taking off for newbies is the stick movement, it should be moved straight up. Any angle to the movements will start turning it and result into tipping off unless pulled up and corrected pretty quickly.